It is desirable that an internal combustion engine be efficient, perform well over a varied load range, have good fuel economy and low atmospheric pollution. One of the types of engines used to achieve this end is the stratified charge engine, where a spark ignites a mixture in a zone where the air/fuel ratio is rich and the charge stratification allows unthrottled operation even at light loads. This tends to give good economy and low emissions of nitrogen oxide (NOX) and carbon monoxide (CO), but the emissions of unburned hydrocarbons (HC) tend to be high. The reason for the high hydrocarbons is that the flame is quenched by the lean air/fuel ratio before all of the fuel is burnt. In an attempt to overcome these problems, the catalytic engine was proposed. With the catalytic engine, fuel is injected directly into the engine combustion chamber and the air/fuel mixture is oxidized and ignited with the aid of a catalyst. The catalytic engine has the advantage of operating at low oxidation or flame temperatures, for example less than 3500.degree. F. for reducing NOX and CO emissions, the catalyst in the engine cleans up the HC emissions without the need for a catalyst in the exhaust system, the engine operates over a wide range of compression ratios and as the fuel oxidation is by catalytic action, rather than spark or compression ignition, the engine will operate on fuels which have poor octane or cetane values. However, the disadvantage of a conventional catalytic engine is that the fuel cannot be carbureted and therefore (a) the engine must have an expensive fuel injection system and (b) gaseous fuels cannot be used.
The present invention overcomes these problems as well as providing an engine that uses a catalyst and allows operations over the load range without throttling and provides an engine which will, because the intake fuel/air mixture is premixed, use any fuel which can be carbureted including gaseous or liquid fuels.